This application claims the priority of Korean Patent Application No. 2002-12759, filed on Mar. 9, 2002, which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an audio coding/decoding system, and more particularly, to a scalable lossless audio coding/decoding apparatus and method which can implement a switching function of a lossy bitstream and a lossless bitstream.
2. Description of the Related Art
Since the use of MP3 techniques started, many other MPEG techniques have been used all over the world. In most MPEG techniques, a very small amount of information is compressed, compared to an original signal, and loss compression usually accompanies data loss. That is, the size of coded information is reduced greatly, but coded information is not completely the same as original sound. However, if an Internet environment is changed from narrow band into wide band and very large capacity transmission lines such as wireless and optical communications are constructed soon, users' desires to receive clearer sound services will increase. Preparing for this trend, a MPEG standardization organization creates an atmosphere for lossless coding standardization, and lossless coding/decoding apparatuses therefor need to be provided. In addition, for a variety of services, a scalable function which can selectively provide a lossy-coded bitstream or lossless-coded bitstream is required.
FIG. 1 shows a block diagram of a conventional lossless coding apparatus. Referring to FIG. 1, a predictor 100 predicts an input audio signal to be input next from an input audio signal INPUT that has been presently input.
An error generating unit 110 compares the input audio signal INPUT with the signal that is predicted by the predictor 100, detects an error between the two signals, and outputs the result of detection as an error signal.
A lossless coding unit 120 lossless codes the error signal that is output from the error generating unit 110 and generates a lossless bitstream.
However, a scalable function cannot be provided by the conventional lossless coding apparatus shown in FIG. 1. In order to provide the scalable function, a lossy bitstream and a lossless bitstream should be generated separately, stored in a separate storage space, and served through switching. In this case, two data should be simultaneously stored in a server's storage unit, and thus a relatively large capacity storage space is necessary, increasing costs.